The present invention relates to a plasma processing apparatus, and in particular to a plasma processing apparatus suitable for formation of various types of films, etching processing of such films, etc., performed in semiconductor element fabrication, etc.
Continued advances have been made in achieving downsizing and higher density integration of semiconductor elements. A microwave plasma processing apparatus is an example of a plasma processing apparatus suitable for use in achieving such downsizing and higher density integration.
A prior-art microwave plasma processing apparatus is described in Japanese Utility Model Publication Laid-Open No. 2-67632. The prior-art microwave plasma processing apparatus includes a vacuum chamber having an upper portion formed by a quartz bell jar, a processing gas introducing tube for introducing a processing gas into the vacuum chamber, a waveguide surrounding the quartz bell jar, a magnetron for generating microwaves connected to the waveguide, a coil for generating a magnetic field disposed around the quartz bell jar outside of the waveguide, a sample table disposed in the vacuum chamber, a high-frequency power supply connected to the sample table, and a movable ground plate disposed in the vacuum chamber around the sample table.
This prior-art microwave plasma processing apparatus operates as follows. A sample is placed on the sample table. A processing gas is introduced into the vacuum chamber through the processing gas introducing tube. Microwaves from the magnetron are introduced into the quartz bell jar through the waveguide while the coil generates a magnetic field in the quartz bell jar. A processing plasma is generated in the quartz bell jar by interaction of the processing gas, the microwaves, and the magnetic field. A high-frequency voltage from the high-frequency power supply is applied to the sample table, thereby applying the high-frequency voltage between the sample table and the ground plate and producing a bias voltage which attracts ions in the processing plasma towards the sample. The height of the ground plate is adjusted to provide a uniform potential distribution.
In this prior-art microwave plasma processing apparatus, no consideration was given to the possibility of metal contamination from the ground plate, and there was a problem that the ground plate was sputtered by ions in the processing plasma, thereby scattering metal particles from the ground plate into the vacuum chamber and contaminating the sample.
The object of the present invention is to provide a plasma processing apparatus capable of performing stable plasma processing of a sample without contaminating the sample with metal particles from a ground plate or other portions of the plasma processing apparatus exposed to a plasma.